Bodily injuries and ailments are commonly treated by applying a nonambient temperature material to the affected area of the body. For example, a low temperature material, typically applied in the form of ice or a cold liquid, may advantageously inhibit swelling in the region of the injury. A high temperature material, typically applied in the form of hot water or an active heating element, may advantageously reduce pain and promote healing. A number of splint devices are known in the art for applying nonambient temperature materials to injured or otherwise ailing areas of the body as evidenced by U.S. Pat. No. 3,548,819 to Davis et al; U.S. Pat. No. 3,901,225 to Sconce; and U.S. Pat. No. 4,706,658 to Cronin. One disadvantage of such devices is that the low temperature materials become warmer as they remain in contact with the body during treatment and the body transfers heat to the low temperature materials. Conversely, high temperature materials become cooler as they transfer heat to the body. This disadvantage can be remedied by periodically replacing the nonambient temperature materials. However, constant replenishment of these materials is cumbersome and inconvenient, and results in periodic treatment temperature fluctuations.
In response to this problem, a number of systems have been developed for continuously circulating a cooling fluid from a low temperature reservoir to a desired body location. Such systems are typified by U.S. Pat. No. 2,726,658 to Chessey; U.S. Pat. No. 3,683,902 to Artemenko et al; and U.S. Pat. No. 4,962,761 to Golden. These fluid circulation systems in general are relatively complex, rendering them costly to manufacture and maintain, as well as difficult to operate. Accordingly, the systems are not practical for widespread use.
U.S. Pat. No. 5,241,951 to Mason et al, incorporated herein by reference, discloses a therapeutic treatment system which rectifies the shortcomings of the above-referenced fluid circulation systems. The therapeutic treatment system of U.S. Pat. No. 5,241,951 is relatively simple, rendering it less costly to manufacture and maintain and enabling greater ease of operation than the prior systems. The system of U.S. Pat. No. 5,241,951 consists essentially of a fluid reservoir, a submersible pump, a pad having an internal fluid flowpath, fluid inlet and outlet lines connecting the pad to the pump and an in-line flow control valve. The system is operated by filling the reservoir with a nonambient temperature treatment fluid and submersing the pump in the fluid. The pad is positioned on the desired treatment region of the user and the pump is activated to deliver fresh treatment fluid from the reservoir to the pad via the fluid inlet line and return spent treatment fluid from the pad to the reservoir via the fluid outlet line. The user regulates the temperature of the pad by manually adjusting the valve to control the flow rate of fluid through the pad.
The system of U.S. Pat. No. 5,241,951 has been shown to provide effective therapeutic treatment to the body. Nevertheless, it has been found that the performance of the system is limited by the submersible pump. In particular, submersible pumps providing the required degree of reliability, i.e., durability and longevity, for the therapeutic treatment application of U.S. Pat. No. 5,241,951 are costly relative to the other system components. In addition, the electric motor of the submersible pump generates heat which is undesirably transferred to the cooling fluid in which the pump is submersed. Also submersion of the electrically-powered pump in the cooling fluid raises safety concerns for the user. Accordingly, the present invention recognizes the need for an improved fluid drive mechanism utilized within a fluid circulation-type therapeutic treatment system. It is an object of the present invention to provide a fluid drive mechanism for a therapeutic treatment system which is effective, safe and reliable, yet relatively inexpensive. It is another object of the present invention to provide a fluid drive mechanism which provides ease of operation and control for the user. These objects and others are achieved in accordance with the invention described hereafter.